This happens for juju 2.8.11, 2.9.11 and 2.9.12. On one of the machines I can see this in machine-0.log:
2021-09-07 08:04:58 ERROR juju.worker.dependency engine.go:671 "broker-tracker" manifold worker returned unexpected error: no container types determined
2021-09-07 08:04:58 INFO juju.worker.authenticationworker worker.go:103 "machine-0" key updater worker started
2021-09-07 08:04:58 INFO juju.container-setup container_initialisation.go:110 initial container setup with ids: [0/lxd/0]
2021-09-07 08:04:58 INFO juju.packaging.manager run.go:88 Running: snap info lxd
2021-09-07 08:04:58 INFO juju.worker.machiner machiner.go:112 "machine-0" started
2021-09-07 08:04:59 INFO juju.container.lxd initialisation_linux.go:300 switching LXD snap channel from 4.0/stable/ubuntu-20.04 to latest/stable
2021-09-07 08:04:59 INFO juju.packaging.manager run.go:88 Running: snap refresh --channel latest/stable lxd
2021-09-07 08:05:18 WARNING juju.container-setup container_initialisation.go:139 not stopping machine agent container watcher due to error: setting up container dependencies on host machine: Not Found
2021-09-07 08:05:18 ERROR juju.container-setup container_initialisation.go:118 starting container provisioner for lxd: setting up container dependencies on host machine: Not Found
2021-09-07 08:05:21 INFO juju.container-setup container_initialisation.go:110 initial container setup with ids: [0/lxd/0]
2021-09-07 08:05:21 INFO juju.packaging.manager run.go:88 Running: snap info lxd
2021-09-07 08:05:22 INFO juju.container.lxd initialisation_linux.go:295 LXD snap is already installed (channel: latest/stable); skipping package installation
Issuing `juju model-config lxd-snap-channel=4.17/stable` prior to deploying anything appears to fix/work around the issue.
Same happened to my deployment as well.